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View Full Version : Volumetric light render settings to get rid of grain?



kojean
05-31-2010, 11:41 PM
I was just trying some fillet plugins and I decided to put a light inside for a quick render. A few hours later...I still haven't figured out how to get rid of the grainy patterns across the image.

The object is very simple and may be the cause of the problem. It's a cube with a few fillets and a flat color surface, with smoothing and double sided enabled, but no thickness. Inside, I placed a spotlight and enabled volumetric light. There is also the default distant light and a point light to fill in the exterior surface.

I'm using radiosity, but not GI. I've tried raising Ray Recursion Limit to 32 and various Ray Precision limits between 1 - 16 and didn't manage to get rid of the grain. I've also gone through a range of combinations of Volumetric Options in the light settings. I also tried switching to Shadow Maps, but that didn't work at all (it was completely blown out and bleeding through the object).

Note: In the Volumetric Options: Enable Texture and and Edit Nodes were enabled by default. I left them as is, since disabling them didn't seem to make a difference in the output.

Can you suggest any settings I can try to remove the grain?

StereoMike
06-01-2010, 02:32 AM
The first that comes to my mind is:
set adaptive sampling (camera) to 0.1 and below (the lower the less grain, but longer rendering times)

UnCommonGrafx
06-01-2010, 04:57 AM
Looks like a render error to me. Like the renderer is trying to do something with the cut apart bits, or the remnants there of.
And only toward the bottom as the side is clean.
Try:
Turn off render lines
Check the texture in the volumetric. Perhaps that's the result of the texture.

kojean
06-01-2010, 07:23 AM
A few more tests.

1. Adaptive Sampling 0.09, Render Lines off, Flares off, flipped normals of bottom surface to point inside, towards light

2. Classic Camera instead of Perspective

3. Extruded bottom filleted surfaces down, the top of the filleted surface normals face inside (up towards light), bottom surface normals face down. All other sufaces (sides of cube, single fillet on the right) are still single-poly with no thickness.

On this last image, the grain is gone in some of the darker areas of the extruded bottom surface, but not in others (even areas only bounded by the same type of thick extruded surfaces).

erikals
06-01-2010, 08:21 AM
try trapcode shine,

fast!

http://www.redgiantsoftware.com/products/all/trapcode-suite/

kojean
06-01-2010, 08:34 AM
try trapcode shine
Thanks, I'm not looking to invest in new tools. I'm just learning and testing in LightWave and trying to troubleshoot the settings.

Latest render: AS threshold 0.04, extruded all sides of the object. Render time: over an hour at this resolution.

erikals
06-01-2010, 08:45 AM
cool, the plugin could render that effect perfectly in 1 sec though :]

kojean
06-01-2010, 09:14 AM
cool, the plugin could render that effect perfectly in 1 sec though :]
So then, how long and what settings would it take for LightWave? And does it require thick, multi-sided geometry or will it work with planar ploys?

Or is this just one of the things LightWave pros usually do in post?

Captain Obvious
06-01-2010, 09:32 AM
First off, turn on jittered sampling. That will get rid of that horrible stepping. Second, use a shadow mapped spot light. That's leagues faster than ray traced shadows. Third, set the anti-aliasing to a decent level (whatever the scene requires; maybe five) and turn off adaptive sampling. Then find a volumetric quality setting that's almost good enough. Then turn on adaptive sampling for the camera, and you're done.


I don't really use a lot of volumetrics in my work, but when I do, I render them in LW. Works fine.



edit: one thing I would recommend is to render the volumetrics in a separate pass, and composit them.

erikals
06-01-2010, 09:32 AM
one of the things LightWave pros usually (basically always) do in post.

06-01-2010, 09:58 AM
One of the things LW Pros who are not into dicking about endlessly in post & who just want to mix stuff up in SpeedEdit find they can do all the time in render.
The bulk of the stuff I do is in 'stage lighting' sort of settings, where the bulk of the light is coming from directed sources (spotlights, dozens of 'em) which are usually desired to have visible beams (volumetrics).
So radiosity stays firmly off, volumetrics have a gentle texture wafting upwards on world co-ordinates, all lights are on shadowmap with a bit of softening.
To play with your object can just be single polys with double sided surfaces, & I'd advise getting the volumetrics looking nice before you play too much with the unimportant surface setting.
Be very aware that any volumetric is being calculated for the entire cone angle (whether shadowed or not) for the entire volumetric length. Vast amounts of calculation are being done on areas with no visible beam in.So in your situation it would be well worth using one light pointing down, just wide enough to fill the cutouts, & then duplicate it and swivel it around to shoot out the side hole, & pull the beam angle down again to just fill the cutouts.

kojean
06-01-2010, 04:44 PM
Captain Obvious and Adrian, thanks very much for the settings tips and the encouragement that this can actually be done in LW. :thumbsup:

I went back to my original, single poly surface object in a new scene, so the angle doesn't quite match. I put a distant light behind the camera for a flat fill to show the surface color. My settings are below and of course it did render faster than any of my previous raytraced shots.

What I ended up with was:

Shadowmap size: 2048
Shadowmap fuzziness: 0 (since I was getting a halo through solid areas of the object)

Antialiasing: 6, Classic, Blue Noise
Adaptive Sampling: 0.09

It's nowhere near perfect and I'm not sure why the borders of the light cone seem to be bleeding through the solid surface, but the volumetric beams are close to the way I intended and the messy bands of grain are gone.

Thanks for all the assistance.

3dWannabe
07-02-2010, 05:35 PM
one of the things LightWave pros usually (basically always) do in post.
Erik - what are the steps one would perform in Lightwave so that volumetric lights could be added in post?

I've got Shine for AE and am learning Fusion for compositing, so I'm quite interested in how to set up volumetric lights properly.

Thanks!

erikals
07-04-2010, 04:28 PM
it's straight forward, just make the areas that you want to glow shine bright
(or texture them white)
then use the Shine AE plugin> done.

p.s.
sometimes you might want to add some additional masking, either in AE, or in LW>AE.

3dWannabe
07-04-2010, 04:44 PM
Ahhh, so you still create the volumetric lights in lightwave.

But, do you create them as volumetric lights, or some other kind of light (or placeholder), after which you make it glow with Shine?

erikals
07-04-2010, 05:07 PM
Ahhh, so you still create the volumetric lights in lightwave.

But, do you create them as volumetric lights, or some other kind of light (or placeholder), after which you make it glow with Shine?

yup :]

3dWannabe
07-04-2010, 05:22 PM
yup :]

Ok, I'm trying to get my head around what would be used instead. For a plug-in to make something glow, there has to be something there in the first place.

It would seem that a light on it's own wouldn't 'create' any pixels that could be acted on by shine.

Are you talking about creating some kind of geometry that would only be used by Shine as a kind of template for where to create the shine (but would be hidden for the final render)?

The original example of the lights coming out of the cube would seem to need some actual light, and have it interact with something?

Would you have a simple example scene for this stand-in that would produce the effect he's trying to accomplish?

erikals
07-04-2010, 06:24 PM
http://www.newtek.com/forums/attachment.php?attachmentid=86126&stc=1&d=1278289424

...For a plug-in to make something glow, there has to be something there in the first place.
yes, in this gif anim i just set the inside to have a 100% illuminated surface

It would seem that a light on it's own wouldn't 'create' any pixels that ...could be acted on by shine.
true, if you use that method you must make the light light up something.

Are you talking about creating some kind of geometry that would only be used by Shine as a kind of template for where to create the shine (but would be hidden for the final render)?
no, but yes, that is another way to go about it.

The original example of the lights coming out of the cube would seem to need some actual light, and have it interact with something?
well AE shine can't interact, so you would have to fake this somehow, by making e.g. a mask.

Would you have a simple example scene for this stand-in that would produce the effect he's trying to accomplish?
First, render an animation (make e.g. the box spin)
Second, Turn box surface black, turn background sky black, turn off lights>
render the same animation, apply Shine to this render in AE. Set the AE layer to screen mode

3dWannabe
07-04-2010, 08:02 PM
http://www.newtek.com/forums/attachment.php?attachmentid=86126&stc=1&d=1278289424

...For a plug-in to make something glow, there has to be something there in the first place.
yes, in this gif anim i just set the inside to have a 100% illuminated surface

It would seem that a light on it's own wouldn't 'create' any pixels that ...could be acted on by shine.
true, if you use that method you must make the light light up something.

Are you talking about creating some kind of geometry that would only be used by Shine as a kind of template for where to create the shine (but would be hidden for the final render)?
no, but yes, that is another way to go about it.

The original example of the lights coming out of the cube would seem to need some actual light, and have it interact with something?
well AE shine can't interact, so you would have to fake this somehow, by making e.g. a mask.

Would you have a simple example scene for this stand-in that would produce the effect he's trying to accomplish?
First, render an animation (make e.g. the box spin)
Second, Turn box surface black, turn background sky black, turn off lights>
render the same animation, apply Shine to this render in AE. Set the AE layer to screen mode
I think you are saying:

1. make a 'beauty' pass.

2. Make a mask pass, and use this mask so that AE Shine only affects areas not masked?

I'm trying to experiment with Janus now, so if I understand you properly, this would be a good experiment. I just wish Shine worked in Fusion.

BTW - thanks a lot for the detailed explanation and sample scene. I'm a bit dense at times, but I'll eventually get it!